In said patent specification is described a ventilation means for evacuating odorous air from the bowl of the water-closet through an internal fan system for discharging to the sewer pipe of the toilet. The fan system comprises a non-return valve, which however is difficult to construct so that it operates well. The fan system must not be dimensioned so that it produces a too high over-pressure in the sewer pipe. As a matter of fact, it is desirable that the non-return valve should operate at such a small pressure difference as 5 mm of water. For obvious reasons, it is important that the non-return valve has an adequate sealing in the closed position. I have found it difficult to make a satisfactorily operating non-return valve.
More specifically, the present invention relates to a combined fan and valve for evacuating air from a space. The combined fan and valve comprises a housing having an inlet and an outlet and a fan wheel and a drive shaft. By means of the combined fan and valve according to the present invention, the above mentioned problem is solved.
In U.S. Pat. No. 4,133,060, a combined fan and valve is described wherein the fan wheel as well as the valve body are affected by the rotation of the drive shaft. When the shaft rotates, the valve body is lifted from its valve seat by means of a centrifugal device and links. However, this device requires that the shaft rotates in order that the centrifugal device shall lift the valve body. Thus, friction will arise at the connection point between the links and the valve body, which due to the fact that it bears upon the valve seat is immobile, which requires that the drive motor have quite a high starting force. A motor having a low starting force can hardly be used in this construction. Moreover, the link means is a potential source of failure and requires maintenance.
It is an object of the present invention to provide a fan having a valve, which has satisfactory sealing in the closed position, but still can be safely opened for ventilation.
Moreover, it is an object of the invention to provide a ventilation means, which can be driven by a simple and weak low voltage motor without any major power consumption, and which is simple to manufacture, has few integral parts and is simple to maintain.